MRI compatible guide wire

ABSTRACT

An improved intracorporeal device such as a guide wire or other guiding member for use within a patient&#39;s body that is at least in part visible under magnetic resonance imaging (MRI) but is not detrimentally affected by the imaging is disclosed. The intercorporeal device has a non-conductive proximal core section, an essentially non-magnetic metallic distal core section that is preferably more flexible than the proximal core section, and that has an MRI visible member or coil in the distal section.

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to the field of medical devices,and more particularly to a guide wire for advancing a catheter or otherintraluminal device within a body lumen in a procedure such aspercutaneous transluminal coronary angioplasty (PTCA) or stent deliverywhich is observed by Magnetic Resonance Imaging (MRI).

[0002] Conventional guide wires for angioplasty and other vascularprocedures usually comprise an elongated core member with one or moretapered sections near the distal end thereof and a flexible body such asa helical coil disposed about the distal portion of the core member. Ashapeable member, which may be the distal extremity of the core memberor a separate shaping ribbon which is secured to the distal extremity ofthe core member, extends through the flexible body and is secured to arounded plug at the distal end of the flexible body. Torquing means areprovided on the proximal end of the core member to rotate, and therebysteer, the guide wire while it is being advanced through a patient'svascular system.

[0003] In a typical PTCA procedure, a guiding catheter having apreformed distal tip is percutaneously introduced into thecardiovascular system of a patient in a conventional Seldinger techniqueand advanced therein until the distal tip of the guiding catheter isseated in the ostium of a desired coronary artery. A guide wire ispositioned within an inner lumen of a dilatation catheter and then bothare advanced through the guiding catheter to the distal end thereof. Theguide wire is first advanced out of the distal end of the guidingcatheter into the patient's coronary vasculature until the distal end ofthe guide wire crosses a lesion to be dilated, then the dilatationcatheter having an inflatable balloon on the distal portion thereof isadvanced into the patient's coronary anatomy over the previouslyintroduced guide wire until the balloon of the dilatation catheter isproperly positioned across the lesion. Once in position across thelesion, the balloon is inflated to a predetermined size with radiopaqueliquid at relatively high pressures (e.g., greater than 4 atmospheres)to press the arteriosclerotic plaque of the lesion against the inside ofthe artery wall and to otherwise expand the inner lumen of the artery.The balloon is then deflated so that blood flow is resumed through thedilated artery and the dilatation catheter can be removed therefrom.

[0004] A major requirement for guide wires is that they have sufficientcolumn strength to be pushed through a patient's vascular system orother body lumen without kinking. However, they must also be flexibleenough to avoid damaging the blood vessel or other body lumen throughwhich they are advanced. Efforts have been made to improve both thestrength and flexibility of guide wires to make them more suitable fortheir intended uses, but these two properties are for the most partdiametrically opposed to one another in that an increase in one usuallyinvolves a decrease in the other.

[0005] Currently, x-ray fluoroscopy is the preferred imaging modalityfor cardiovascular interventional procedures because no other imagingmethod has the temporal or spatial resolution provided by fluoroscopy.However, x-ray imaging has many drawbacks for both the patient and theclinician. The iodinated contrast agents employed in x-ray fluoroscopyare nephrotoxic with a low but measurable incidence of short-term renalfailure and allergic reactivity. The ionizing radiation from the x-rayfluoroscopy can be an issue for the patient during protracted orrepeated interventions and is a daily issue for the interventionalistand staff who must cope with the burden of personal dose monitoring andwearing lead shielding.

[0006] The use of MRI for observing interventional procedures has beenperformed for balloon angioplasty and stent placement. The use of thisimaging modality is quite attractive because it eliminates some of theproblems inherent with x-ray imaging. On the other hand, conventionalguide wires which are suitable for x-ray fluoroscopy are not suitablefor use in MRI observed interventional procedures due to their magneticattraction, large magnetic susceptibility artifact, and potentialheating when exposed to RF energy.

[0007] What has been needed and heretofore unavailable is a guide wirewhich is safe and compatible for use in conjunction with MRI. Thepresent invention satisfies these and other needs.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to an intracorporeal devicesuch as a guide wire which is safe, compatible and readily visible withMRI. An intracorporeal device embodying features of the inventionpreferably has an elongated member with an electrically non-conductiveproximal section, an essentially non-magnetic distal core section, and ametallic coil disposed about and secured to the distal core section witha small magnetic susceptibility to act as an MRI visible marker. Thatis, the coil or a marker thereon has a magnetic susceptibility thatfacilitates the observation thereof within the patient under MRI.

[0009] The distal end of the proximal non-conductive core section andthe proximal end of the non-magnetic but conductive distal core sectioncan be secured together by any non-conductive means including polymericor metallic sleeves so long as the joint between these members resultsin a torque transmitting relationship therebetween.

[0010] The selection of materials for component parts of theintracorporeal device, such as a guide wire, including the proximalsection, the distal section and the MRI visible member secured to thedistal section are based upon the mechanical and physical propertiesneeded for the intended use. The materials from which the MRI compatibledevice is made need to overcome three basic factors: magnetic attractionof magnetic members, RF heating effects of conductive members, andvisualization under MRI.

[0011] Forming the proximal section from non-conductive, non-metallicmaterial and the distal section and MRI visible member from non-magneticmaterials resolves the magnetic attraction of these members during MRI.The non-conductive, non-metallic nature of the proximal core section andthe length of the distal core section alone or in conjunction with theMRI visible member resolve the RF heating of these members. Controllingthe level of magnetic susceptibility of the material from which the MRIvisible member is formed resolves the visualization issue.

[0012] Suitable materials for the non-conductive proximal section of theintracorporeal device include optical fibers (single or a bundle offibers), fiberglass, carbon fiber-epoxy composites, composites oforiented polyethylene fiber (e.g., Spectra®), composites of polyaramidefiber (e.g., Kelvar®) and composites of these materials with engineeringresins such as polysulfone, polyethersulfone, polyetherimide,vinylester, cyanate ester, phenolic, polyurethane, polyimide andpolyetheretherketone. The MRI visible member or marker and preferablyalso the distal section are formed of suitable non-magnetic materialsthat may be electrically conductive. Suitable materials include one ormore metallic materials selected from the group consisting of platinum,nitinol, niobium, titanium, tantalum, zirconium, iridium, aluminum,silver, gold, indium, and alloys thereof.

[0013] The distal core section and the tip coil are formed of suitablenon-magnetic conductive materials having the correct amount of magneticsusceptibility artifact for accurate imaging. The volumetric magneticsusceptibility suitable for visualization under MRI for these structuresis less than or equal to about 280×10⁻⁶ (SI), and preferably less thanabout 245×10⁻⁶ (SI).

[0014] The intracorporeal devices embodying features of the presentinvention are in part readily visible under MRI and they have desirablecharacteristics for performing intracorporeal procedures. These andother advantages of the invention will become more apparent from thefollowing detailed description thereof when taken in conjunction withthe following exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a side elevational view, partially in section, of aguide wire that embodies features of the present invention.

[0016]FIG. 2 is an enlarged, side elevational view, partially insection, of the junction between the proximal and distal core sectionsof the guide wire shown in FIG. 1 taken within line 2-2.

[0017]FIG. 3 is a cross-sectional view of the guide wire shown in FIG. 1taken along the line 3-3.

[0018]FIG. 4 is a cross-sectional view of the guide wire shown in FIG. 1taken along line 4-4.

[0019]FIG. 5 is a cross-sectional view of the guide wire connectionshown in FIG. 2 taken along the line 5-5.

[0020]FIG. 6 is a cross-sectional view of the guide wire shown in FIG. 1taken along line 6-6.

[0021]FIG. 7 is a side elevational view, partially in section, of analternative distal core section having non-conductive junctions betweenconductive core segments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] FIGS. 1-6 illustrate an embodiment of an MRI compatible guidewire 10 embodying features of the present invention that is used in apatient's body lumen, such as an artery or vein. The guide wire 10generally comprises an elongated, relatively non-conductive proximalcore section 11, a relatively short, non-magnetic, metallic distal coresection 12, a polymeric connecting element 13 securing together thedistal end 14 of the proximal core section 11 and the proximal end 15 ofthe distal core section 12. A helically shaped metallic coil 16, formedat least in part of non-magnetic material; is disposed about and securedto the distal core section 12. The coil 16 is secured at its distal endby a rounded body 17 of solder, weldment, or adhesive, at anintermediate location by a mass 24 of solder or adhesive, and at itsproximal end by a mass 19 of solder, adhesive or other suitable materialthat joins the coil 16 to the distal core section 12.

[0023] The guide wire 10 shown in FIG. 1 generally has conventionalintravascular guide wire features and the particular embodiment shown iscommonly called a “floppy” guide wire due to the shaping ribbon 23 whichextends from the distal core section 12 to the rounded mass 17. Thedistal end of the shaping ribbon 23 is secured to the end of the coil 16by the mass 17 and the proximal end thereof is secured by intermediatemass 24 of connecting material which also secures an intermediateportion of the coil 16 to the distal core section 12. The distal coresection 12 optionally has at least one tapered section 25 with smallertransverse dimensions in the distal direction. The rounded distal tip 26of the distal core section 12 is so configured to prevent the end of thedistal core section from extending through the spacing between the turnsof the coil 16 when the guide wire 10 passes through tortuous anatomy.

[0024] The polymeric connecting element 13, which is shown in detail inFIG. 2, is a polymeric member that is disposed about and secured to theundulated distal end 20 of the proximal core section 11 and theundulated proximal end 21 of the distal core section 12. This embodimentof the connector element 13 generally has a cylindrical exterior 22 thathas an outer diameter about the same as the outer diameter of the coil16 and the outer diameter of the proximal core section 11. The ends 20and 21 of the proximal core section 11 and the distal core section 12may be given an undulated shape as shown in FIG. 2 to provide amechanical interlock or friction fit with the polymeric material of theconnecting element 13 which is secured about the ends 20, 21.

[0025] The connection between the ends 20 and 21 of the proximal anddistal core sections 11 and 12, respectively, may be made by positioningthe distal end 20 of the proximal core section 11 and the proximal end21 of the distal core section 12 in close proximity to each other withinthe interior of a mold which preferably has a cylindrical interiormolding surface of the desired dimensions of the exterior surface 22 ofthe connecting member 13. Polymerizable or otherwise hardenablenon-conductive material is introduced into the interior of the mold andpolymerized or otherwise hardened into a polymeric or other non-metallicmass about the ends 20 and 21 so as to fix the ends within theconnecting element 13. The hardenable non-conductive material formingthe connection between the proximal and distal core sections 11 and 12is sufficiently strong to facilitate torque transmission between thesecore sections.

[0026] Suitable non-magnetic, and preferably polymeric materials for theconnecting element 13 include one or more thermoplastic polymericmaterials such as a polyester, polyetheretherketone, ABS, and epoxymaterials or co-polymers orblends thereof. The polymeric materials maybe blends of a variety of polymeric materials. The polymeric material ispreferably selected so that the connecting element 13 holds the two coresections together to effect torque transmission and to provide a smoothtransition between the proximal and distal core sections 11 and 12,respectively.

[0027] The proximal section 11 of one embodiment of the guide wire 10 isfabricated from metals such as work hardened 304V stainless steel. Inorder to have similar tracking, torque, and push properties, proximalsections of polymeric and composite materials would ideally have similarproperties. One important property to match is stiffness both laterallyand axially while hardness is of lesser importance. To achieve thepreferred properties of a guide wire, any proximal shaft of a polymericmaterial would be a composite. Further, the polymer component may be athermoset or a thermoplastic. Exemplary of common thermosets includeepoxy, polyester, vinylester, cyanate ester, phenolic, polyurethane, andpolyimide. Suitable fiber reinforcement materials include fiberglass,s-glass, e-glass, graphite, Kevlar®, Twaron®, Nomex®, Spectra®,polyaramid, carbon, boron, and boron nitride.

[0028] Fiberglass components may also be used in fabricating the guidewire, recognizing that fiberglass is typically a composite of apolyester resin with a glass fiber reinforcement. Guide wires fabricatedentirely from fiberglass, however, do not have the functional advantagesof a distal metallic section 12 and metallic tip coil 17.

[0029] Composite guide wire structures of fiber reinforced polymericmaterials may be made by methods of extrusion, pultrusion, injectionmolding, transfer molding, flow encapsulation, fiber winding on amandrel, or lay-up with vacuum bagging. Epoxy resins are available froma variety of manufacturers including Ciba Specialty Chemicals, ShellChemical, Dow Chemical, and Gougeon Brothers, Inc. Sources of carbonfiber include Hexcel Corp., Amoco, Toho, Rayon, and Toray. Exemplary ofnon-composite materials for the non-conductive proximal section 11include glass fiber optics (available from Coming Glass and SeikoInstruments, Inc.) and ceramics.

[0030] The examples set forth in detail below illustrate the fabricationof a composite proximal shaft of a guide wire in accordance with thepresent invention. In the first exemplary embodiment, a compositeproximal shaft is fabricated with IM7 carbon fibers (available fromHexcel Corp.) and an Epon epoxy resin system (available from ShellCorp.). Using pultrusion, a shaft of 67 volume percent carbon fiber isfabricated. A 20 cm distal section of nitinol is affixed to the shaftusing a sleeve joint. A tip coil of 90/10 tantalum/tungsten alloy isattached by soldering to the distal end of the nitinol section.

[0031] In the second exemplary embodiment, a composite proximal shaft isfabricated of Victrex® PEEK 450CA30 (30% carbon reinforced) byextrusion. Optional bands of palladium are attached to the shaft at 10cm intervals to function as passive paramagnetic susceptibility markers.The 20 cm distal metallic shaft is fabricated of CP (commercially pure)titanium (Wah-Chang). A 90/10 platinum/iridium tip coil is attached viasoldering to the titanium section.

[0032] As seen in FIG. 1, one embodiment of a guide wire 10 havingfeatures of the present invention generally includes an elongated coremember with an electrically non-conductive proximal core section 11, ametallic distal core section 12 with low magnetic susceptibility, and ametallic tip coil 27 extending from the distal end of the distal coresection 12.

[0033] The non-electrically conductive proximal core section 11 is MRIsafe with regard to both attractive forces and RF heating effects. Thisdistal core section 12 between the non-conductive proximal core section11 and the tip coil 27 is analogous to the distal nitinol section of aconventional guide wire. Its maximum safe length can be estimated fromthe magnetic field strength of the MRI scanner. At 1.5T, antenna theorypredicts that a guide wire can behave as a dipole antenna beginning at alength of 23 inches (about 58 cm).

[0034] Preferably, the metallic tip coil 27 and the distal core section12 (the conductive members) are connected with a non-conductiveinsulator so that they do not act in concert as a single dipole antenna.If the metallic tip coil 27 and the distal core section 12 are separatedby a non-conductive material 13, then the length of the distal coresection 12 can be up to 23 cm in a magnetic field of 1.5T. Without theinsulator, the 23 cm length applies to the total length of the tip coil27 and the distal core section 12.

[0035] As the RF frequency utilized is linearly proportional to the MRIscanner field strength, lower field strengths of 1.0T and 0.5T couple atconductor member lengths of 35 cm and 69 cm, respectively. So at a lowermagnetic field strength of 1.5T, a preferred range for the length of theconductive member is less than 29 cm. A more preferred range of thelength of the conductive member is less than 23 cm. The minimumpractical length of the conductive section is determined by the lengthof a functional guide wire tip coil which is approximately 3 cm. Thesemaximum safe lengths are inversely proportional to the magnetic fieldstrength.

[0036] The highest field strength MRI scanners in routine clinical useat the present time operate at 3T. At this strength, a preferredconductor length is less than approximately 14.4 cm, and a morepreferred conductor length is less than approximately 11.5 cm. Thus, asthe MRI scanner field strength increases, the safe length of theconductive members decreases.

[0037] Accordingly, the conductive member in one embodiment has a lengthof about L≦43.5/B_(o), where “L” represents the electrically conductivelength in centimeters, and “B_(o)” represents the scanner magnetic fieldin Tesla. In a more preferred embodiment, the conductive member has alength of about L≦34.5/B_(o). The experimental and theoreticalfoundation for these values may be found in the work of Liu et al.,Journal of magnetic Resonance Imaging, Vol. 12, pp. 75-78 (2000), andNitz et al., Journal of Magnetic Resonance Imaging, Vol. 13, pp. 105-114(2001), the contents of which are incorporated herein by reference.

[0038]FIG. 7 illustrates another embodiment in which the length of themetallic distal core section (conductive member) is limited. Inparticular, the distal core section 12 may be formed in multiplemetallic segments 31 and 32 separated by a non-conductive joint 33. Thisconstruction provides a longer metallic distal core section with each ofthe metallic segments being kept short enough so as to not be heatedwhen subjected to the magnetic fields generated by the MRI to providegreater length distal sections.

[0039] The electrical conductivity of the non-conductive proximal coresection 11 is electrical resistivity expressed in micro-ohm-cm. Thehigher the value for electrical resistivity, the more resistance for thematerial of the proximal core section. Based on research using nitinolguide wires, for example, it has been found that at about 100micro-ohm-cm, a nitinol guide wire is conductive enough to heat in anMRI scanner. However, little research has been done examining howconductive a long wire can be in an MRI and still avoid heating. Modelsof this effect have considered resistance of the wire to be negligible.The minimum resistivity for the non-conductive proximal core section isestimated to be approximately 0.01 ohm-cm.

[0040] The coil 16 may also be formed by two separate coil segments: adistal coil segment 27 which is formed of a non-magnetic material havingthe requisite magnetic susceptibility to provide MRI visibility, and aproximal coil segment 28 which may be made of another material havingother desirable properties such as radiopacity. Additionally, the distalcoil segment 27 of the coil 16 may be stretched about 10 to about 30% inlength as shown in FIG. 1 to provide increased flexibility.

[0041] The elongated proximal core section 11 may be an optical fiberwhich should be provided with a coating 30 of lubricous material such asa fluoropolymer, polytetrafluoroethylene sold under the trademarkTeflon® by Du Pont de Nemours & Co. Other suitable lubricous coatingsinclude fluoropolymers, hydrophilic coatings and polysiloxane coatings.

[0042] The overall length of the guide wire 10 will vary depending uponthe procedure and the MRI compatibility parameters mentioned above, butfor percutaneous intravascular procedures the guide wire is generallyabout 100 to about 200 cm in length. Most commercially available guidewires for adult coronary use come in lengths of 175 cm and 195 cm. Theouter diameter of the guide wire ranges from about 0.006 to 0.018 inch(0.15-0.45 mm) for coronary use. Larger diameter guide wires, e.g. up to0.035 inch (0.89 mm) or more may be employed in peripheral arteries andother body lumens. The length of the distal core section can range fromabout 1 to about 30 cm, depending upon the flexibility and otherproperties including MRI imaging characteristics desired in the finalproduct. The helical coil 16 may be about 3 to about 45 cm in length,preferably about 5 to about 30 cm and may have an outer diameter aboutthe same size as the outer diameter of the elongated proximal coresection 11. The helical coil 16 is preferably made from wire about 0.001to about 0.003 inch (0.025-0.08 mm) in diameter, typically about 0.002inch (0.05 mm). The shaping ribbon 21 and the flattened distal section29 of distal core section 12 can have generally rectangular shapedtransverse cross-sections which usually have dimensions of about 0.0005to about 0.006 inch (0.013-0.152 mm), and preferably about 0.001 by0.003 inch (0.025-0.076 mm).

[0043] In an embodiment of the present invention, the distal coresection 12 is made of a metal or alloy material which has a volumetricmagnetic susceptibility of less than about 280×10⁻⁶ (SI), and preferablyless than about 245×10⁻⁶ (SI). Metals that meet this criteria and theirrespective volumetric magnetic susceptibility are set forth in thefollowing table. While the distal core section 12 needs to beessentially non-magnetic, it does not necessarily require the volumetricmagnetic susceptibility set forth above which provides visibility underMRI. VOLUMETRIC MAGNETIC MATERIAL SUSCEPTIBILITY (×10⁻⁶ (SI)) Platinum279 Nitinol 245 Niobium 237 Titanium 182 Tantalum 178 Zirconium 109Iridium 37.5 Aluminum 20.7 Silver −24 Gold −34 Indium −51

[0044] Various polymeric connecting elements 13 embodying features ofthe invention generally have outer diameters from about 0.006 inch toabout 0.02 inch (0.15-0.51 mm), and preferably about 0.1 to about 0.014inch (mm) for coronary guide wires. The overall length of the connectingelement 13 may range from about 0.25 to about 3 cm, and typically rangesabout 0.75 to about 1.5 cm. Naturally, the connecting elements for guidewires for other medical applications and treatment sites may havedimensions different than that described above.

[0045] The proximal core section 11 is formed of a non-conductivematerial such as an optical fiber (e.g., a single fiber or a bundle offibers), carbon fiber-epoxy composites, composites of orientedpolyethylene fiber (e.g., Spectra®), composites of polyaramide fiber(e.g., Kelvar®), and composites of these materials with engineeringresins such as polyaryetherketone, polyphenylenesulfide, polyimide andpolyetheretherketone. Other suitable non-conductive materials may beused for the proximal core section.

[0046] The guide wire embodying features of the invention may bepercutaneously introduced into a patient's blood vessel, such as thefemoral artery, and advanced within the patient's vasculature under MRIso as to be able to observe the coil at the guide wire distal coresection which acts as an MRI visible marker member to ensure that theguide wire or other intracorporeal device is disposed at a desiredlocation within the patient's vasculature. Once the distal portion ofthe guide wire is in place at the desired location, a therapeutic ordiagnostic device may be advanced over the inplace guide wire until theoperative portion of the intracorporeal device is positioned. to performa therapeutic or diagnostic procedure in a conventional fashion.

[0047] While the description of embodiments having features of theinvention has been directed primarily herein to guide wires suitable forguiding other devices within a patient's body, those skilled in the artwill recognize that these features may also be utilized in otherintracorporeal devices such as electrophysiology catheters, pacing leadsand the like. References to other modifications and improvements can bemade to the invention without departing from the scope of the appendedclaims.

[0048] To the extent not otherwise described herein, the materials andmethods of construction and the dimensions of conventionalintracorporeal devices such as intravascular guide wires may be employedwith a device embodying features of the present invention. Moreover,features disclosed with one embodiment may be employed with otherdescribed embodiments. Additionally, reference to the terms “members,”“elements,” “sections” and terms of similar import in the claims whichfollow shall not be interpreted to invoke the provisions of 35 U.S.C. §112 (paragraph 6) unless reference is expressly made to the term “means”followed by an intended function.

What is claimed is:
 1. An elongated intracorporeal member that is MRIcompatible, comprising: an elongated core having an electricallynon-conductive proximal core section and an essentially non-magneticmetallic distal core section; a non-conductive connecting elementsecuring together a distal end of the proximal core section and aproximal end of the distal core section; and a metallic coil that is atleast in part disposed about the distal core section.
 2. Theintracorporeal member of claim 1, wherein a distal end of the proximalcore section and a proximal end of the distal core section have anundulated shape to effect a mechanical interlock with the non-conductiveconnecting element.
 3. The intracorporeal member of claim 1, wherein themetallic coil includes a material having a volumetric magneticsusceptibility enabling observation of the intracorporeal member whensubjected to MRI.
 4. The intracorporeal member of claim 1, wherein atleast one of the distal core section and the metallic coil is formed ofa material having a volumetric magnetic susceptibility of less thanabout 280×10⁻⁶ (SI).
 5. The intracorporeal member of claim 1, wherein atleast one of the distal core section and the metallic coil is formed ofa material having a volumetric magnetic susceptibility of less thanabout 245×10⁻⁶ (SI).
 6. The intracorporeal member of claim 1, whereinthe distal core section includes one or more materials selected from thegroup consisting of platinum, nitinol, niobium, titanium, zirconium,iridium, aluminum, silver, gold, indium, and alloys thereof.
 7. Theintracorporeal member of claim 1, wherein the distal core section isdimensioned to exhibit negligible heating when exposed to MRI.
 8. Theintracorporeal member of claim 1, wherein the distal core sectionincludes a continuous metallic portion having a length L≦43.5/B_(o). 9.The intracorporeal member of claim 1, wherein the distal core sectionincludes a continuous metallic portion having a length L≦34.5/B_(o). 10.The intracorporeal member of claim 1, wherein the distal core sectionand the metallic coil define a length L≦34.5/B_(o).
 11. Theintracorporeal member of claim 1, wherein the distal core sectionincludes superelastic nitinol.
 12. The intracorporeal member of claim 1,wherein the connecting element is formed at least in part of one or morethermoplastic polymeric materials selected from the group consisting ofpolyester, polyetheretherketone, ABS, epoxy, copolymers, and blendsthereof.
 13. The intracorporeal member of claim 1, wherein theconnecting element is selected to enable the connecting member to holdthe proximal core section and distal core section together to effecttorque transmission and to provide a smooth transition between therespective sections.
 14. The intracorporeal member of claim 1, whereinthe distal core section is formed at least in part of one or morematerials selected from the group consisting of platinum, nitinol,niobium, titanium, tantalum, zirconium, iridium, aluminum, silver, gold,indium, and alloys thereof.
 15. The intracorporeal member of claim 1,wherein the proximal core section is formed of a non-conductive materialselected from the group consisting of optical fibers, carbon fiber-epoxycomposites, oriented polyethylene fiber composites, polyaramide fibercomposites, resins, and combinations thereof.
 16. The intracorporealmember of claim 15, wherein the resins are materials selected from thegroup consisting of polyaryetherketone, polyphenylenesulfide, polyimide,and polyetheretherketone.
 17. An elongated guide wire for intraluminaldelivery of therapeutic or diagnostic devices, comprising: an elongatedcore having an electrically non-conductive, non-metallic proximal coresection having proximal and distal ends; an essentially non-magneticmetallic distal core section having proximal and distal ends; a torquetransmitting junction between the distal end of the proximal coresection and the proximal end of the distal core section; and anessentially non-magnetic MRI visible coil that is at least in partsecured to the distal core section.
 18. The guide wire of claim 17,wherein the non-magnetic coil is formed of a material having avolumetric magnetic susceptibility that facilitates observation of theelement when subjected to MRI.
 19. The guide wire of claim 18, whereinthe coil includes a material having a volumetric magnetic susceptibilityof less than about 280×10⁻⁶ (SI).
 20. The guide wire of claim 18,wherein the coil includes a material having a volumetric magneticsusceptibility of less than about 245×10⁻⁶ (SI).
 21. The guide wire ofclaim 17, wherein the distal core section has a continuous metallicportion of not more than L≦43.5/B_(o).
 22. The guide wire of claim 17,wherein the distal core section has a continuous metallic portion of notmore than L≦34.5/B_(o).
 23. The guide wire of claim 17, wherein thedistal core section has at least two longitudinally disposed segmentsseparated by a non-conductive junction.
 24. The guide wire of claim 17,wherein the coil is formed at least in part of one or more materialsselected from the group consisting of platinum, nitinol, niobium,titanium, tantalum, zirconium, iridium, aluminum, silver, gold, indium,and alloys thereof.
 25. A method of performing an intracorporealprocedure within a patient, comprising: providing a guide wire having anelongated core with a non-conductive proximal core section, anessentially non-magnetic distal core section, and an MRI visiblemagnetic marker on the distal core section; introducing the guide wireinto a body lumen of the patient; advancing the guide wire therein underMRI until the MRI visible magnetic member on the distal core section isdisposed within a desirable location within the patient; and advancing atherapeutic or diagnostic device over the guide wire until an operativeportion of the device is disposed at a location in which a therapeuticor diagnostic procedure is to be performed.
 26. A method of performingan intracorporeal procedure within a patient, comprising: providing anelongated intracorporeal device having an elongated non-conductiveproximal section, a non-magnetic distal section and an MRI visiblemagnetic marker on the distal section; introducing the intracorporealdevice into a patient's body; advancing the intracorporeal devicetherein under MRI until the MRI visible magnetic marker on the distalcore section is disposed within a desirable location within the patient;and performing a therapeutic or diagnostic procedure.